1. Field of the Invention
The invention relates to a method and apparatus for converting heat energy into work energy and also for pumping heat energy from a low temperature level to a high temperature level. A characteristic feature of the invention is in the use of a working medium which is subjected to a cyclic operation, each comprises of a melting step and a solidification step operated under two pressure levels and at two temperature levels.
2. Brief Description of the Prior Art
In a conventional external heat engine, a working medium, such as water, is generally subjected to a high pressure vaporization operation to absorb heat at a high temperature level, the resulting high pressure vapor is depressurized through a turbine to produce work, the exhaust vapor from the turbine is condensed at a low pressure to reject heat at a low temperature level, and finally the condensate is returned to the high pressure vaporization operation described.
In a conventional heat pump, a refrigerator on an air conditioner, a working medium, such as ammonia and Freon, is vaporized at a low temperature level, the low pressure medium vapor is then compressed to a high pressure, the resulting pressurized medium vapor is condensed under the high pressure to release heat at a high temperature level and finally the condensed medium is returned to the low pressure vaporization operation. The efficiencies of these conventional heat engines and heat pumps are generally less than 70% of the theoretical thermodynamic efficiencies.
BRIEF DESCRIPTION OF THE PRESENT INVENTION
The present invention introduces a heat engine, or a heat pump, in which the working medium used is subjected alternatively to solidification and melting operations. A working medium so used is referred to as an S/L type working medium. In a new heat engine with a non-aqueous S/L type medium, the medium is melted under a high temperature T.sub.H and a high pressure P.sub.H to absorb heat and is solidified under a low temperature T.sub.L and a low pressure P.sub.L to release heat. Since the non-aqueous medium expands as it is melted under the high pressure and contracts as it is solidified under the low pressure, the system does work to its surrounding. Since water expands on solidification and contracts on melting in a new heat engine with an aqueous medium, the medium is melted under a high temperature and a low pressure to absorb heat and is solidified under a low temperature and a high pressure to release heat. Since the aqueous medium expands under the high pressure as it is solidified and contracts under the low pressure as it is melted, the system does work to the surrounding. The operation of a heat pump is just the reverse operation of a heat engine. A new engine comprises of multiplicity of longitudinal conduits which are connected through a first check valve to a high pressure zone and through a second check valve to a low pressure zone. Referring to a heat engine utilizing a non-aqueous S/L medium, medium liquid in an amount equivalent to volume expansion associated with the high pressure melting operation is discharged to the high pressure zone through the first check valve from each conduit during a melting step and an equivalent amount of medium enters each conduit during a solidification step through the second check valve. The medium discharged under the high pressure may be depressurized through a hydraulic motor to do work and becomes low pressure medium. For a heat engine utilizing an aqueous S/L medium, medium liquid in an amount equivalent to volume expansion associated with high pressure solidification is discharged to the high pressure zone through the first check valve from each conduit during a solidification step and an equivalent amount of medium enters each conduit during a melting step through the second check valve. A new heat pump is about the same as a new heat engine. The operation of a heat pump is the reverse operation of that of a heat engine and work has to be supplied to the system.